A sum-frequency study of the two-dimensional phase transition in a monolayer of undecanol on water

Sum-frequency (SF) vibrational spectra are presented of monolayers of 1-undecanol on water in the vicinity of the first-order phase transition at 28°C. A combined analysis of SF and ellipsometric data permits the calculation of the molecular tilt and area per molecule in the high-temperature phase. The SF spectra demonstrate that the monolayer remains highly conformationally ordered above the phase transition.